Organization of data in table form is a time-honored and useful method of data representation. While columns of data are trivially generated by computer through formatted output, even simple tasks like keeping titles aligned with the data columns are not trivial, and the one-shot solutions one comes up with tend to be particularly hard to maintain. Text::Table allows you to create and maintain tables that adapt to alignment requirements as you use them.

The process is simple: you create a table (a Text::Table object) by describing the columns the table is going to have. Then you load lines of data into the table, and finally print the resulting output lines. Alignment of data and column titles is handled dynamically in dependence on the data present.

In the simplest case, if all you want is a number of (untitled) columns, you create an unspecified table and start adding data to it. The number of columns is taken from the first line of data.

To specify a table you specify its columns. A column description can contain a title and alignment requirements for the data, both optional. Additionally, you can specify how the title is aligned with the body of a column, and how the lines of a multiline title are aligned among themselves.

The columns are collected in the table in the order they are given. On data entry, each column corresponds to one data item, and in column selection columns are indexed left to right, starting from 0.

Each title can be a multiline string which will be blank-filled to the length of the longest partial line. The largest number of title lines in a column determines how many title lines the table has as a whole, including the case that no column has any titles.

On output, columns are separated by a single blank. You can control what goes between columns by specifying separators between (or before, or after) columns. Separators don't contain any data and don't count in column indexing. They also don't accumulate: in a sequence of only separators and no columns, only the last one counts.

Table data is entered line-wise, each time specifying data entries for all table columns. A bulk loader for many lines at once is also available. You can clear the data from the table for re-use (though you will more likely just create another table).

The title contains the combined titles from the table columns, if any. Its content never changes with a given table, but it may be spread out differently on the page through alignment with the data.

The body contains the data lines, aligned column-wise as specified, and left-aligned with the column title.

Each of these is arranged like a Perl array (counting from 0) and can be accessed in portions by specifying a first line and the number of following lines. Also like an array, giving a negative first line counts from the end of the area. The whole table, the title followed by the body, can also be accessed in this manner.

The subdivisions are there so you can repeat the title (or parts of it) along with parts of the body on output, whether for screen paging or printout.

A rule line is also available, which is the horizontal counterpart to the separator columns you specify with the table. It is basically a table line as it would appear if all data entries in the line were empty, that is, a blank line except for where the column separators have non-blank entries. If you print it between data lines, it will not disrupt the vertical separator structure as a plain blank line would. You can also request a solid rule consisting of any character, and even one with the non-blank column separators replaced by a character of your choice. This way you can get the popular representation of line-crossings like so:

Each column specification is a single scalar. Columns can be either proper data columns or column separators. Both can be specified either as (possibly multi-line) strings, or in a more explicit form as hash-refs. In the string form, proper columns are given as plain strings, and separators are given as scalar references to strings. In hash form, separators have a true value in the field is_sep while proper columns don't have this field.

A column is given as a column title (any number of lines), optionally followed by alignment requirements. Alignment requirements start with a line that begins with an ampersand "&". However, only the last such line counts as such, so if you have title lines that begin with "&", just append an ampersand on a line by itself as a dummy alignment section if you don't have one anyway.

What follows the ampersand on its line is the alignment style (like left, right, ... as described in "Alignment"), you want for the data in this column. If nothing follows, the general default auto is used. If you specify an invalid alignment style, it falls back to left alignment.

The lines that follow can contain sample data for this column. These are considered for alignment in the column, but never actually appear in the output. The effect is to guarantee a minimum width for the column even if the current data doesn't require it. This helps dampen the oscillations in the appearance of dynamically aligned tables.

$title contains the title lines and $sample the sample data. Both can be given as a string or as an array-ref to the list of lines. $align contains the alignment style (without a leading ampersand), usually as a string. You can also give a regular expression here, which specifies regex alignment. A regex can only be specified in the hash form of a column specification.

In hash form you can also specify how the title of a column is aligned with its body. To do this, you specify the keyword align_title with left, right or center. Other alignment specifications are not valid here. The default is left.

align_title also specifies how the lines of a multiline title are aligned among themselves. If you want a different alignment, you can specify it with the key align_title_lines. Again, only left, right or center are allowed.

Do not put other keys than those mentioned above (title, align, align_title, align_title_lines, and sample) into a hash that specifies a column. Most would be ignored, but some would confuse the interpreter (in particular, is_sep has to be avoided).

A separator must be given as a reference to a string (often a literal, like \' | '), any string that is given directly describes a column.

It is usually just a (short) string that will be printed between table columns on all table lines instead of the default single blank. If you specify two separators (on two lines), the first one will be used in the title and the other in the body of the table.

$title is the separator to be used in the title area and $body the one for the body. If only one is given, it will be used for both. If none is given, a blank is used. If one is shorter than the other, it is blank filled on the right.

The value of is_sep must be set to a true value, this is the distinguishing feature of a separator.

The original documentation to Text::Aligner contains all the details on alignment specification, but here is the rundown:

The possible alignment specifications are left, right, center, num and point (which are synonyms), and auto. The first three explain themselves.

num (and point) align the decimal point in the data, which is assumed to the right if none is present. Strings that aren't numbers are treated the same way, that is, they appear aligned with the integers unless they contain a ".". Instead of the decimal point ".", you can also specify any other string in the form num(,), for instance. The string in parentheses is aligned in the data. The synonym point for num may be more appropriate in contexts that deal with arbitrary strings, as in point(=>) (which might be used to align certain bits of Perl code).

regex alignment is a more sophisticated form of point alignment. If you specify a regular expression, as delivered by qr//, the start of the match is used as the alignment point. If the regex contains capturing parentheses, the last submatch counts. [The usefulness of this feature is under consideration.]

auto alignment combines numeric alignment with left alignment. Data items that look like numbers, and those that don't, form two virtual columns and are aligned accordingly: num for numbers and left for other strings. These columns are left-aligned with each other (i.e. the narrower one is blank-filled) to form the final alignment.

This way, a column that happens to have only numbers in the data gets num alignment, a column with no numbers appears left-aligned, and mixed data is presented in a reasonable way.

Besides creating tables from scratch, they can be created by selecting columns from an existing table. Tables created this way contain the data from the columns they were built from.

This is done by specifying the columns to select by their index (where negative indices count backward from the last column). The same column can be selected more than once and the sequence of columns can be arbitrarily changed. Separators don't travel with columns, but can be specified between the columns at selection time.

You can make the selection of one or more columns dependent on the data content of one of them. If you specify some of the columns in angle brackets [...], the whole group is only included in the selection if the first column in the group contains any data that evaluates to boolean true. That way you can de-select parts of a table if it contains no interesting data. Any column separators given in brackets are selected or deselected along with the rest of it.

creates a table with the columns specified. A column can be proper column which contains and displays data, or a separator which tells how to fill the space between columns. The format of the parameters is described under "Column Specification". Specifying an invalid alignment for a column results in a warning if these are allowed.

If no columns are specified, the number of columns is taken from the first line of data added to the table. The effect is as if you had specified Text::Table->new( ( '') x $n), where $n is the number of columns.

creates a table from the listed columns of the table $tb, including the data. Columns are specified as integer indices which refer to the data columns of $tb. Columns can be repeated and specified in any order. Negative indices count from the last column. If an invalid index is specified, a warning is issued, if allowed.

As with "new()", separators can be interspersed among the column indices and will be used between the columns of the new table.

If you enclose some of the arguments (column indices or separators) in angle brackets [...] (technically, you specify them inside an arrayref), they form a group for conditional selection. The group is only included in the resulting table if the first actual column inside the group contains any data that evaluate to a boolean true. This way you can exclude groups of columns that wouldn't contribute anything interesting. Note that separators are selected and de-selected with their group. That way, more than one separator can appear between adjacent columns. They don't add up, but only the rightmost separator is used. A group that contains only separators is never selected. [Another feature whose usefulness is under consideration.]

returns the width (in characters) of the table. All table lines have this length (not counting a final "\n" in the line), as well as the separator lines returned by $tb->rule() and $b->body_rule(). The width of a table can potentially be influenced by any data item in it.

returns the start position and width of the $i-th column (counting from 0) of the table. If $i is negative, counts from the end of the table. If $i is larger than the greatest column index, an imaginary column of width 0 is assumed right of the table.

$col1, ..., $colN are scalars that correspond to the table columns. Undefined entries are converted to '', and extra data beyond the number of table columns is ignored.

Data entries can be multi-line strings. The partial strings all go into the same column. The corresponding fields of other columns remain empty unless there is another multi-line entry in that column that fills the fields. Adding a line with multi-line entries is equivalent to adding multiple lines.

Every call to add() increases the body height of the table by the number of effective lines, one in the absence of multiline entries.

Every argument to load() represents a data line to be added to the table. The line can be given as an array(ref) containing the data items, or as a string, which is split on whitespace to retrieve the data. If an undefined argument is given, it is treated as an empty line.

The three methods table(), title(), and body() are very similar. They access different parts of the printable output lines of a table with similar methods. The details are described with the table() method.

The first call returns all the lines in the table. The second call returns one line given by $line_number. The third call returns $n lines, starting with $line_number. If $line_number is negative, it counts from the end of the array. Unlike the select() method, table() (and its sister methods title() and body()) is protected against large negative line numbers, it truncates the range described by $line_number and $n to the existing lines. If $n is 0 or negative, no lines are returned (an empty string in scalar context).

A rule is a line of table width that can be used between table lines to provide visual horizontal divisions, much like column separators provide vertical visual divisions. In its basic form (returned by the first call) it looks like a table line with no data, hence a blank line except for the non-blank parts of any column-separators. If one character is specified (the second call), it replaces the blanks in the first form, but non-blank column separators are retained. If a second character is specified, it replaces the non-blank parts of the separators. So specifying the same character twice gives a solid line of table width. Another useful combo is $tb->rule( '-', '+'), together with separators that contain a single nonblank "|", for a popular representation of line crossings.

rule() uses the column separators for the title section if there is a difference.

If callbacks are specified instead of the characters, then they receive the index of the section of the rule they need to render and its desired length in characters, and should return the string to put there. The indexes given are 0 based (where 0 is either the left column separator or the leftmost cell) and the strings will be trimmed or extended in the replacement.

The warnings() method is used to control the appearance of warning messages while tables are manipulated. When Text::Table starts, warnings are disabled. The default action of warnings() is to turn warnings on. The other possible arguments are self-explanatory. warnings() can also be called as an object method ($tb->warnings( ...)).

The code is open to the world, and available for you to hack on. Please feel free to browse it and play with it, or whatever. If you want to contribute patches, please send me a diff or prod me to pull from your repository :)